Various chairs and armrest assemblies have been designed to support a user's forearm and wrist and can be adjusted vertically. However many of these supports only allow for limited movement of the armrest and requires a great deal of pressure to adjust vertically.
For example, U.S. Pat. No. 4,270,798 issued on Jun. 2, 1991 to Coach & Car Equipment Corporation, discloses an armrest which is pivotable through a vertical plane between a horizontally extending, arm-supporting position and an upwardly extending position alongside the seat back. The armrest is also pivotable, in response to a predetermined outwardly directed force against the armrest, through a horizontal plane, between the above-described arm-supporting position and a position in which the armrest extends rearwardly from the seat back.
U.S. Pat. No. 4,429,918 which issued on Feb. 7, 1984 to Syntex (U.S.A.) Inc. relates to an operatory stool.
U.S. Pat. No. 4,438,975 issued to Dentsply Research & Development Corp. on Mar. 27, 1984 relates to a post relatively fixed with respect to seat 16, unless vertical adjustment is desired by means of the hand screw.
U.S. Pat. No. 5,382,079 was issued on Jan. 17, 1995 to Chromcraft Revington, Inc. relates to the adjustable arm including an arm body having an upper housing and a sleeve portion which is slidably mounted on the generally vertical section of the arm frame assembly for vertical adjustment of the chair arm. A latching assembly is connected to the frame assembly and arm body for releasably locking the arm body in a plurality of vertical positions on the frame assembly. Lastly, an actuator, integral with the latching assembly, is provided for disabling the latching assembly.
U.S. Pat. No. 5,393,124 issued to Gary K. Neil on Feb. 28, 1995 relates to an armrest assembly for a chair comprising, an upper arm, support shaft structure associated with the upper arm, the support shaft presenting an axis of rotation for rotational movement of the upper arm, a structure associated with the chair for receiving the support shaft for relative rotational movement of the upper arm relative the receiving structure about the axis, and a structure for radially rotating the position of the upper arm about the axis of rotation to multiple positions as required for the user's comfort.
U.S. Pat. No. 4,907,835 issued on Mar. 13, 1990 to Charles Salter relates to a removable arm rest apparatus for use in a truck cab utilizing an upright tubing structure and a flat arm support member projecting normally outward therefrom.
U.S. Pat. No. 4,917,438 issued on Apr. 17, 1990 to Flight Equipment & Engineering Limited relates to an adjustable-width seating for passenger-carrying vehicles.
U.S. Pat. No. 5,439,267 issued on Aug. 8, 1995 to Steelcase Inc. relates to a chair including a tubular arm support, an armrest, a lateral adjustment mechanism and a vertical height adjustment mechanism. The lateral adjustment mechanism includes a plurality of nested slides. One slide is connected to the vertical height adjustment mechanism. An uppermost slide supports the arm rest. The slides are adjustable laterally with respect to each other to position the armrest with respect to the chair. The vertical height adjustment mechanism includes a tubular liner insertable into the arm support. The liner defines a bore and a plurality of vertically spaced notches or grooves. A latch tube telescopes with the bore of the liner. An upper end of the latch tube is connected to the lateral adjustment mechanism. The latch is pivotally positioned within the latch tube. The latch includes a latch end moveable into and out of engagement with the notches. An actuator engages the latch to move it between locked and unlocked positions.
U.S. Pat. No. 3,339,873 issued on Sep. 5, 1967 to D. H. Hale relates to a stool with a vertically moveable seat wherein a tank disposed under the seat at the top of a hollow reciprocable piston rod and containing air under pressure to accommodate, upon opening a valve between the hollow interior of the piston rod and the interior of the surrounding cylinder by actuation of a plate under the seat above the tank, (a) elevation of the piston rod, the actuating table, the seat and the tank, when the seat is not occupied, by a flow of fluid from the interior of the piston rod through and around a disc flow control into the interior of the cylinder under force of said pressure, and (b) lowering of the piston rod, the actuating plate, the seat and the tank, when the seat is occupied, by flow of fluid from the interior of the cylinder through the disc flow control to the hollow interior of the piston rod counter to said pressure.
U.S. Pat. No. 3,547,394 issued on Dec. 15, 1970, to Cramer Industries, Inc. relates to vertically adjustable articles of furniture and more particularly to an apparatus for adjusting the height of a chair seat.
U.S. Pat. No. 3,711,054 issued to Fritz Bauer on Jan. 16, 1973 relates to a lifting device for the stepless height adjustment of the seat surface member of a chair, stool or the like.
U.S. Pat. No. 4,940,202 issued on Jul. 10, 1990 to Stabilus GmbH relates to a stepless adjustable vertical movement device for chairs, tables or the like articles, which comprises a blockable gas spring which is arranged in a telescopic unit consisting of a telescopic tube and a guide tube and is connected by means of a self-locking taper connection on the one hand with the chair seat or a similar article of adjustable height and on the other hand with a foot part, a simple replacement of the gas spring is to be provided, with security against unintended unscrewing of the gas spring is guaranteed.
U.S. Pat. No. 4,940,202 issued on Nov. 13, 1990 to Suspa Compart Aktiengesellschaft relates to an adjustable-length column for chairs, tables or the like having an upright tube and a gas spring disposed in it. The piston rod of the gas spring is supported against a bottom plate of the upright tube. To assure support of the bottom plate in the face of extremely strong forces in the axial direction of the column at little manufacturing expense, the rim of the upright tube is bent inward approximately semicircularly in cross section. The bottom plate is supported on the end face of the rim.
Each of the prior art devices referred to above present relatively complicated structures having relatively limited mobility of the armrest. Large forces are also required to activate the adjustable-length columns that are located in the seat portions of many of the prior art devices. An advantage to the present invention is the ease in which the armrest assembly can be manufactured, assembled and repaired due to the lack of complexity of the structures. Another advantage is that the amount of pressure that is required to activate the armrest assembly is dramatically reduced, thereby requiring the user to exert only a minimal force for the armrest to be activated.